This invention relates to electrical interconnection of stacked circuit boards.
As space requirements have become more stringent, the need has arisen for providing stacked arrays of printed circuit boards with integrated circuit (IC) and other components mounted thereon. In addition to the requirement for electrical interconnection between the boards, a spacer is required to ensure sufficient board separation to accommodate the components and to allow for cooling air flow (see, e.g., U.S. Pat. No. 5,049,982 issued to Lee et al.).
For large board separations (i.e., 15 mm or more) and high density connections (i.e., less than 1.5 mm pitch) a high aspect ratio is required for the conductors interconnecting the boards. This aspect ratio is difficult to meet with standard electrical connectors. Further, the lack of precisely parallel board surfaces can result in connection failures.
U.S. Pat. No. 5,049,982, cited above, shows interconnection of circuit boards using layers of conductive polymer interconnect (CPI) material and a spacer therebetween. The spacers comprise pieces of printed circuit board with metal-coated vias therethrough for providing the electrical interconnection.
U.S. Pat. No. 4,514,784 issued to Williams et al. employs pins inserted in a connector block to interconnect circuit boards.
U.S. Pat. No. 5,160,268 issued to Hakamian provides interconnection between boards by means of a connector which includes an array of spring contacts on the top and bottom of the connector. Use of threaded inserts allows the connector to float between the stacked boards.
In U.S. Pat. No. 5,154,621 issued to Legrady, interconnection between boards is achieved by conductive pins mounted within undulating sockets, while the boards are separated by a spacer plate made of conductive material which is grounded to provide shielding.
These approaches, while generally adequate, are not easily implemented when high density interconnection and large board separations are required.